ORIGINAL: MichaelT.

But with all of that said, in low light situations, a 50mm will allow you to see a hair better than a 40 mm when comparing two like scopes. Yes, EURO glass is better than Japaneese glass for all intents and purposes .... across the board..... but if you are comparing a Nikon and a Simmons, that is not a fair comparison. If you are comparing a Zeiss and a Tasco ..... thats not fair .... but comparing to alike scopes of same manufaturer, model , andstyle, but one with a 40 and one with a 50 .... the 50 will see better. NOT A LOT BETTER .... BUT JUST A HAIR BETTER......